Hi I am back:
I don't think this has anything to do with the theme, so I changing the status to resolved. And anyway I have a workaround.
Something is stripping out all line breaks and multiple spaces together when I post. That's can't be the theme, I would think, more like my browser or text editor. I use ff on ubuntu 8.04, and opera was the same.
So after playing around with it I found a workaround, which will do nicely. Not sure if it will work for everyone, as I removed all the text-handling plugins, including TinyMCE.
Anyway, the solution I got from these board is between paragraphs, where I would normally put the break tag, I put this:
<div><br class="webkit-block-placeholder" /></div><div>